Misfiring Cyl 2/4/6 ?? 2015 LR4

Salanizi

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ECT sensors can cause rough idle -messes with the air fuel ratio.

I will definetly be replacing those, as I do not trust my mechanic as the car idles smoothly upon startup, only when warm (after some driving) does it become rough

My simple understanding of course thinks that if an internal engine part was at fault, wouldnt it idle roughly the whole time?

Is there anything else other than the 2 ECT sensors i should replace whilst im there at it?
 

jlglr4

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It’s probably idling rough after warm-up because that is when the car goes into closed-loop fuel control, adjusting the fuel supply based on feedback from the o2 sensors and other sensors involved in the fuel control system. On cold start, it is operating off the fuel table and ignoring the sensor readings.

But, yes, that seems to point away from things like piston slap or crankshaft issues, and towards something in the fuel/air control or supply systems. Is that supercharger still making clunking noises?
 

greiswig

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Again,if neither you nor your mechanic have a way to read the codes or the real-time parameters, you are likely to spend more money in guesswork replacement parts than you would by just buying the GAP tool and replacing the parts that a subsequent diagnosis might recommend.

In spite of how helpful people are on this forum, I’m not sure how much more help you can get from it without some data to point us to. To me it feels as though you are asking us if a part might cause shaky idle when warmed up, and the answer is probably “yes”, not because it is likely that part but more because there are a lot of different parts that might cause a shaky idle.
 

Salanizi

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It’s probably idling rough after warm-up because that is when the car goes into closed-loop fuel control, adjusting the fuel supply based on feedback from the o2 sensors and other sensors involved in the fuel control system. On cold start, it is operating off the fuel table and ignoring the sensor readings.

But, yes, that seems to point away from things like piston slap or crankshaft issues, and towards something in the fuel/air control or supply systems. Is that supercharger still making clunking noises?

Yes, supercharger is still making the deep metal clunk noise, both my mechanic and the local LR dealer say thats its probably sloppy vortices and cannot be remedied save for replacing the supercharger


I order 2 ECT sensors and a MAP sensor as well to replace in 2 weeks once im back from vacation. I hope this fixes things as indeed when the vehicle is running without the sensor feedback it is very smooth


Anything else i should look into?
 

Salanizi

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Again,if neither you nor your mechanic have a way to read the codes or the real-time parameters, you are likely to spend more money in guesswork replacement parts than you would by just buying the GAP tool and replacing the parts that a subsequent diagnosis might recommend.

In spite of how helpful people are on this forum, I’m not sure how much more help you can get from it without some data to point us to. To me it feels as though you are asking us if a part might cause shaky idle when warmed up, and the answer is probably “yes”, not because it is likely that part but more because there are a lot of different parts that might cause a shaky idle.

Hello Sir

I truely appreciate your insight with my issue, however i am not inclined to buy a GAP tool because of two things:

1. My mechanic has a simple OBD reader which i can use when im there replacing stuff lol

2. I do not plan of keeping the car more than 18 more months

3. I think I already replaced 90% of the components that could cause a shaky idle when warmed up, and do believe that whatever 10% left would cost less than a GAP tool -that is under the assumption that i do not have internal engine damage

Cylinders on bank 2 were compression tested, results as follows:

Cyl. 4 = 120psi
Cyl. 5 = 110psi
Cyl. 6 = 120psi
 

jlglr4

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If your sc is not outputting the expected boost, that might be messing up your idle as well. Not to mention that particles of metal might be going into your cylinders if the sc blades really are contacting each other. I find it hard to imagine slop in the blade shafts is really the problem.

When does the sc make the clunking noise? all the time? just at startup or shut down, or when hitting the gas hard or releasing throttle?
 

Salanizi

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If your sc is not outputting the expected boost, that might be messing up your idle as well. Not to mention that particles of metal might be going into your cylinders if the sc blades really are contacting each other. I find it hard to imagine slop in the blade shafts is really the problem.

When does the sc make the clunking noise? all the time? just at startup or shut down, or when hitting the gas hard or releasing throttle?

Only at idle, once i accelerate or raise the RPM it goes away
 

jlglr4

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If it sounds something like marbles rattling, that’s just the isolator/coupler. Known issue and easy fix, but won’t affect performance.

Otherwise, I still wonder if it might be the bypass valve. If there is something wrong with the bypass, I think it will affect performance.
 

Salanizi

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If it sounds something like marbles rattling, that’s just the isolator/coupler. Known issue and easy fix, but won’t affect performance.

Otherwise, I still wonder if it might be the bypass valve. If there is something wrong with the bypass, I think it will affect performance.

Replaced the isolator, didnt fix things

I dont think theres an issue with boost though...remember my manifold pressure was almost identical to yours
 

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